text: /*
   **********************************************************************
   *   Copyright (C) 2005-2012, International Business Machines
   *   Corporation and others.  All Rights Reserved.
   **********************************************************************
   */
  
  #include "unicode/utypes.h"
  
  #if !UCONFIG_NO_CONVERSION
  
  #include "cstring.h"
  
  #include "csr2022.h"
  #include "csmatch.h"
  
  U_NAMESPACE_BEGIN
  
  #define ARRAY_SIZE(array) (sizeof array / sizeof array[0])
  
  /**
   * Matching function shared among the 2022 detectors JP, CN and KR
   * Counts up the number of legal and unrecognized escape sequences in
   * the sample of text, and computes a score based on the total number &
   * the proportion that fit the encoding.
   * 
   * 
   * @param text the byte buffer containing text to analyse
   * @param textLen  the size of the text in the byte.
   * @param escapeSequences the byte escape sequences to test for.
   * @return match quality, in the range of 0-100.
   */
  int32_t CharsetRecog_2022::match_2022(const uint8_t *text, int32_t textLen, const uint8_t escapeSequences[][5], int32_t escapeSequences_length) const
  {
      int32_t i, j;
      int32_t escN;
      int32_t hits   = 0;
      int32_t misses = 0;
      int32_t shifts = 0;
      int32_t quality;
  
      i = 0;
      while(i < textLen) {
          if(text[i] == 0x1B) {
              escN = 0;
              while(escN < escapeSequences_length) {
                  const uint8_t *seq = escapeSequences[escN];
                  int32_t seq_length = (int32_t)uprv_strlen((const char *) seq);
  
                  if (textLen-i >= seq_length) {
                      j = 1;
                      while(j < seq_length) {
                          if(seq[j] != text[i+j]) {
                              goto checkEscapes;
                          }
  
                          j += 1;
                      }
  
                      hits += 1;
                      i += seq_length-1;
                      goto scanInput;
                  }
                  // else we ran out of string to compare this time.
  checkEscapes:
                  escN += 1;
              }
  
              misses += 1;
          }
  
          if( text[i]== 0x0e || text[i] == 0x0f){
              shifts += 1;
          }
  
  scanInput:
          i += 1;
      }
  
      if (hits == 0) {
          return 0;
      }
  
      //
      // Initial quality is based on relative proportion of recongized vs.
      //   unrecognized escape sequences. 
      //   All good:  quality = 100;
      //   half or less good: quality = 0;
      //   linear inbetween.
      quality = (100*hits - 100*misses) / (hits + misses);
  
      // Back off quality if there were too few escape sequences seen.
      //   Include shifts in this computation, so that KR does not get penalized
      //   for having only a single Escape sequence, but many shifts.
      if (hits+shifts < 5) {
          quality -= (5-(hits+shifts))*10;
      }
  
      if (quality < 0) {
          quality = 0;
      }
  
      return quality;
  }
  
  
  static const uint8_t escapeSequences_2022JP[][5] = {
      {0x1b, 0x24, 0x28, 0x43, 0x00},   // KS X 1001:1992
      {0x1b, 0x24, 0x28, 0x44, 0x00},   // JIS X 212-1990
      {0x1b, 0x24, 0x40, 0x00, 0x00},   // JIS C 6226-1978
      {0x1b, 0x24, 0x41, 0x00, 0x00},   // GB 2312-80
      {0x1b, 0x24, 0x42, 0x00, 0x00},   // JIS X 208-1983
      {0x1b, 0x26, 0x40, 0x00, 0x00},   // JIS X 208 1990, 1997
      {0x1b, 0x28, 0x42, 0x00, 0x00},   // ASCII
      {0x1b, 0x28, 0x48, 0x00, 0x00},   // JIS-Roman
      {0x1b, 0x28, 0x49, 0x00, 0x00},   // Half-width katakana
      {0x1b, 0x28, 0x4a, 0x00, 0x00},   // JIS-Roman
      {0x1b, 0x2e, 0x41, 0x00, 0x00},   // ISO 8859-1
      {0x1b, 0x2e, 0x46, 0x00, 0x00}    // ISO 8859-7
  };
  
  #if !UCONFIG_NO_NON_HTML5_CONVERSION
  static const uint8_t escapeSequences_2022KR[][5] = {
      {0x1b, 0x24, 0x29, 0x43, 0x00}   
  };
  
  static const uint8_t escapeSequences_2022CN[][5] = {
      {0x1b, 0x24, 0x29, 0x41, 0x00},   // GB 2312-80
      {0x1b, 0x24, 0x29, 0x47, 0x00},   // CNS 11643-1992 Plane 1
      {0x1b, 0x24, 0x2A, 0x48, 0x00},   // CNS 11643-1992 Plane 2
      {0x1b, 0x24, 0x29, 0x45, 0x00},   // ISO-IR-165
      {0x1b, 0x24, 0x2B, 0x49, 0x00},   // CNS 11643-1992 Plane 3
      {0x1b, 0x24, 0x2B, 0x4A, 0x00},   // CNS 11643-1992 Plane 4
      {0x1b, 0x24, 0x2B, 0x4B, 0x00},   // CNS 11643-1992 Plane 5
      {0x1b, 0x24, 0x2B, 0x4C, 0x00},   // CNS 11643-1992 Plane 6
      {0x1b, 0x24, 0x2B, 0x4D, 0x00},   // CNS 11643-1992 Plane 7
      {0x1b, 0x4e, 0x00, 0x00, 0x00},   // SS2
      {0x1b, 0x4f, 0x00, 0x00, 0x00},   // SS3
  };
  #endif
  
  CharsetRecog_2022JP::~CharsetRecog_2022JP() {}
  
  const char *CharsetRecog_2022JP::getName() const {
      return "ISO-2022-JP";
  }
  
  UBool CharsetRecog_2022JP::match(InputText *textIn, CharsetMatch *results) const {
      int32_t confidence = match_2022(textIn->fInputBytes, 
                                      textIn->fInputLen, 
                                      escapeSequences_2022JP, 
                                      ARRAY_SIZE(escapeSequences_2022JP));
      results->set(textIn, this, confidence);
      return (confidence > 0);
  }
  
  #if !UCONFIG_NO_NON_HTML5_CONVERSION
  CharsetRecog_2022KR::~CharsetRecog_2022KR() {}
  
  const char *CharsetRecog_2022KR::getName() const {
      return "ISO-2022-KR";
  }
  
  UBool CharsetRecog_2022KR::match(InputText *textIn, CharsetMatch *results) const {
      int32_t confidence = match_2022(textIn->fInputBytes, 
                                      textIn->fInputLen, 
                                      escapeSequences_2022KR, 
                                      ARRAY_SIZE(escapeSequences_2022KR));
      results->set(textIn, this, confidence);
      return (confidence > 0);
  }
  
  CharsetRecog_2022CN::~CharsetRecog_2022CN() {}
  
  const char *CharsetRecog_2022CN::getName() const {
      return "ISO-2022-CN";
  }
  
  UBool CharsetRecog_2022CN::match(InputText *textIn, CharsetMatch *results) const {
      int32_t confidence = match_2022(textIn->fInputBytes,
                                      textIn->fInputLen,
                                      escapeSequences_2022CN,
                                      ARRAY_SIZE(escapeSequences_2022CN));
      results->set(textIn, this, confidence);
      return (confidence > 0);
  }
  #endif
  
  CharsetRecog_2022::~CharsetRecog_2022() {
      // nothing to do
  }
  
  U_NAMESPACE_END
  #endif
  